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Metrizable spaces homeomorphic to the hyperspace of nonblockers of singletons of a continuum 连续统单子的非阻塞子的超空间同胚的可度量空间
IF 0.6 4区 数学
Topology and its Applications Pub Date : 2025-02-01 DOI: 10.1016/j.topol.2024.109151
David Maya, Fernando Orozco-Zitli, Emiliano Rodríguez-Anaya
{"title":"Metrizable spaces homeomorphic to the hyperspace of nonblockers of singletons of a continuum","authors":"David Maya,&nbsp;Fernando Orozco-Zitli,&nbsp;Emiliano Rodríguez-Anaya","doi":"10.1016/j.topol.2024.109151","DOIUrl":"10.1016/j.topol.2024.109151","url":null,"abstract":"<div><div>A <em>continuum</em> is a nondegenerate compact connected metric space. The hyperspace of all nonempty closed subsets of a continuum <em>X</em> topologized by the Hausdorff metric is denoted by <span><math><msup><mrow><mn>2</mn></mrow><mrow><mi>X</mi></mrow></msup></math></span>. Given a continuum <em>X</em>, the subspace <span><math><mrow><mi>NB</mi></mrow><mo>(</mo><msub><mrow><mi>F</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo><mo>)</mo></math></span> of <span><math><msup><mrow><mn>2</mn></mrow><mrow><mi>X</mi></mrow></msup></math></span> consists of all elements <span><math><mi>A</mi><mo>∈</mo><msup><mrow><mn>2</mn></mrow><mrow><mi>X</mi></mrow></msup><mo>−</mo><mrow><mo>{</mo><mi>X</mi><mo>}</mo></mrow></math></span> such that for each <span><math><mi>x</mi><mo>∈</mo><mi>X</mi><mo>−</mo><mi>A</mi></math></span>, the union of all subcontinua of <em>X</em> containing <em>x</em> and contained in <span><math><mi>X</mi><mo>−</mo><mi>A</mi></math></span> is a dense subset of <em>X</em>. The members of <span><math><mrow><mi>NB</mi></mrow><mo>(</mo><msub><mrow><mi>F</mi></mrow><mrow><mn>1</mn></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo><mo>)</mo></math></span> are called nonblocker subsets of the singletons of the continuum <em>X</em>. In this paper, we show that each proper nonempty open subset <em>U</em> of a compact metric space can be embedded in a continuum <em>X</em> such that <em>U</em> and the hyperspace of nonblocker subsets of <em>X</em> are homeomorphic. This answers a question posed by J. Camargo, F. Capulín, E. Castañeda-Alvarado and D. Maya.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"360 ","pages":"Article 109151"},"PeriodicalIF":0.6,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143133240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Fréchet spaces, ω-Rudin property and Smyth power spaces fracimchet空间,ω-Rudin性质和Smyth幂空间
IF 0.6 4区 数学
Topology and its Applications Pub Date : 2025-01-28 DOI: 10.1016/j.topol.2025.109235
Xiaoquan Xu , Hualin Miao , Qingguo Li
{"title":"Fréchet spaces, ω-Rudin property and Smyth power spaces","authors":"Xiaoquan Xu ,&nbsp;Hualin Miao ,&nbsp;Qingguo Li","doi":"10.1016/j.topol.2025.109235","DOIUrl":"10.1016/j.topol.2025.109235","url":null,"abstract":"<div><div>For a <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>-space <em>X</em>, let <span><math><mi>K</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span> be the poset of all nonempty compact saturated subsets of <em>X</em> endowed with the Smyth order (i.e., the reverse inclusion order). The Smyth power poset <span><math><mi>K</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span> equipped with the upper Vietoris topology is called the Smyth power space of <em>X</em> and is denoted by <span><math><msub><mrow><mi>P</mi></mrow><mrow><mi>S</mi></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo></math></span>. This paper is mainly devoted to discuss some properties of Fréchet spaces from the viewpoint of intersection of topology and domain theory. We prove that if the sobrification (especially, the Hoare power space) of a <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>-space <em>X</em> is a Fréchet space, then <em>X</em> is an <em>ω</em>-Rudin space. Hence every <em>ω</em>-well-filtered space for which its sobrification (especially, its Hoare power space) is a Fréchet space is sober, and every second-countable <em>ω</em>-well-filtered space is sober. We also show that if the Smyth power space of a <span><math><msub><mrow><mi>T</mi></mrow><mrow><mn>0</mn></mrow></msub></math></span>-space <em>X</em> is a Fréchet space, then the Scott topology is coarser than the upper Vietoris topology on <span><math><mi>K</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span>, whence if <em>X</em> is additionally well-filtered, then the topology of Smyth power space <span><math><msub><mrow><mi>P</mi></mrow><mrow><mi>S</mi></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo></math></span> is the Scott topology of <span><math><mi>K</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span>. Moreover, if <em>X</em> is a second-countable <em>ω</em>-well-filtered space, then the topology of <span><math><msub><mrow><mi>P</mi></mrow><mrow><mi>S</mi></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo></math></span> is the Scott topology of <span><math><mi>K</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span>.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"363 ","pages":"Article 109235"},"PeriodicalIF":0.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143139108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Every Lindelöf scattered subspace of a Σ-product of real lines is σ-compact 实线的Σ-product的每一个Lindelöf离散子空间都是σ-紧的
IF 0.6 4区 数学
Topology and its Applications Pub Date : 2025-01-28 DOI: 10.1016/j.topol.2025.109234
Antonio Avilés , Mikołaj Krupski
{"title":"Every Lindelöf scattered subspace of a Σ-product of real lines is σ-compact","authors":"Antonio Avilés ,&nbsp;Mikołaj Krupski","doi":"10.1016/j.topol.2025.109234","DOIUrl":"10.1016/j.topol.2025.109234","url":null,"abstract":"<div><div>We prove that every Lindelöf scattered subspace of a Σ-product of first-countable spaces is <em>σ</em>-compact. In particular, we obtain the result stated in the title. This answers some questions of Tkachuk (2022) <span><span>[9]</span></span>.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"363 ","pages":"Article 109234"},"PeriodicalIF":0.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143139137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
The L-algebras related to prime spectra of Bézout domains and abelian ℓ-groups 与bsamzout域和阿贝尔群的素谱有关的l -代数
IF 0.6 4区 数学
Topology and its Applications Pub Date : 2025-01-28 DOI: 10.1016/j.topol.2025.109231
Wolfgang Rump
{"title":"The L-algebras related to prime spectra of Bézout domains and abelian ℓ-groups","authors":"Wolfgang Rump","doi":"10.1016/j.topol.2025.109231","DOIUrl":"10.1016/j.topol.2025.109231","url":null,"abstract":"<div><div>The <em>ℓ</em>-spectrum problem asks for a topological characterization of the prime spectrum of a Bézout domain (equivalently, the inverse prime spectrum of an abelian <em>ℓ</em>-group). While a general solution is out of reach, the analogous problem for the maximal spectrum of a Bézout domain was solved in a previous article. An analysis of the <em>ℓ</em>-spectrum problem by means of <em>L</em>-algebras is given. If the prime spectrum is an Esakia space, the known explicit solutions will be compared and related to a finitely additive measure that connects two fundamental classes of <em>L</em>-algebras. The abelian <em>ℓ</em>-groups constructed by several authors from an Esakia space are shown to be structure groups of <em>L</em>-algebras. The <em>L</em>-algebraic method is then extended to more general prime spectra, which leads to a new sufficient criterion for spectral spaces to be representable as prime spectra of Bézout domains.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"362 ","pages":"Article 109231"},"PeriodicalIF":0.6,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
From λ-hollow frames to λ-repletions in W: II. λ-repletions in W W: II从λ空心框架到λ填充。λ-在W中的重复
IF 0.6 4区 数学
Topology and its Applications Pub Date : 2025-01-27 DOI: 10.1016/j.topol.2025.109233
Richard N. Ball , Anthony W. Hager , Joanne Walters-Wayland
{"title":"From λ-hollow frames to λ-repletions in W: II. λ-repletions in W","authors":"Richard N. Ball ,&nbsp;Anthony W. Hager ,&nbsp;Joanne Walters-Wayland","doi":"10.1016/j.topol.2025.109233","DOIUrl":"10.1016/j.topol.2025.109233","url":null,"abstract":"&lt;div&gt;&lt;div&gt;In this article we analyze the fine structure of the essential extensions of an object of &lt;strong&gt;W&lt;/strong&gt;, the category of divisible archimedean lattice ordered groups with designated weak units. In particular, we show that an object &lt;em&gt;G&lt;/em&gt; has an ordinally indexed sequence &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mo&gt;{&lt;/mo&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;mo&gt;}&lt;/mo&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;δ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; of essential extensions with the following features.&lt;span&gt;&lt;span&gt;&lt;img&gt;&lt;/span&gt;&lt;/span&gt;&lt;ul&gt;&lt;li&gt;&lt;span&gt;•&lt;/span&gt;&lt;span&gt;&lt;div&gt;&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; is (isomorphic to) the identity function on &lt;em&gt;G&lt;/em&gt;.&lt;/div&gt;&lt;/span&gt;&lt;/li&gt;&lt;li&gt;&lt;span&gt;•&lt;/span&gt;&lt;span&gt;&lt;div&gt;For every &lt;span&gt;&lt;math&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;mo&gt;&gt;&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; is an essential extension of &lt;em&gt;G&lt;/em&gt; into a &lt;strong&gt;W&lt;/strong&gt;-object which is of the form &lt;span&gt;&lt;math&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mi&gt;L&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; for some frame &lt;em&gt;L&lt;/em&gt;, and which is &lt;em&gt;λ&lt;/em&gt;-replete for some &lt;em&gt;λ&lt;/em&gt;.&lt;/div&gt;&lt;/span&gt;&lt;/li&gt;&lt;li&gt;&lt;span&gt;•&lt;/span&gt;&lt;span&gt;&lt;div&gt;Every such extension is (isomorphic to) &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;α&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; for a unique &lt;em&gt;α&lt;/em&gt;.&lt;/div&gt;&lt;/span&gt;&lt;/li&gt;&lt;li&gt;&lt;span&gt;•&lt;/span&gt;&lt;span&gt;&lt;div&gt;&lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;δ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; is (isomorphic to) the maximal essential extension of &lt;em&gt;G&lt;/em&gt;.&lt;/div&gt;&lt;/span&gt;&lt;/li&gt;&lt;li&gt;&lt;span&gt;•&lt;/span&gt;&lt;span&gt;&lt;div&gt;If &lt;span&gt;&lt;math&gt;&lt;mi&gt;λ&lt;/mi&gt;&lt;mo&gt;≤&lt;/mo&gt;&lt;mi&gt;ν&lt;/mi&gt;&lt;mo&gt;≤&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;δ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; then &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;ν&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt; factors through &lt;span&gt;&lt;math&gt;&lt;msubsup&gt;&lt;mrow&gt;&lt;mi&gt;τ&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;G&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;λ&lt;/mi&gt;&lt;/mrow&gt;&lt;/msubsup&gt;&lt;/math&gt;&lt;/span&gt;.&lt;/div&gt;&lt;/span&gt;&lt;/li&gt;&lt;/ul&gt; Here a &lt;strong&gt;W&lt;/strong&gt;-object is said to be &lt;em&gt;λ&lt;/em&gt;-replete if it has the following equivalent properties.&lt;ul&gt;&lt;li&gt;&lt;span&gt;•&lt;/span&gt;&lt;span&gt;&lt;div&gt;Every &lt;em&gt;λ&lt;/em&gt;-generated &lt;strong&gt;W&lt;/strong&gt;-kernel is a polar.&lt;/div&gt;&lt;/span&gt;&lt;/li&gt;&lt;li&gt;&lt;span&gt;•&lt;/span&gt;&lt;span&gt;&lt;div&gt;Every proper &lt;em&gt;λ&lt;/em&gt;-generated &lt;strong&gt;W&lt;/strong&gt;-kernel of &lt;em&gt;G&lt;/em&gt; is contained in a proper polar.&lt;/div&gt;&lt;/span&gt;&lt;/li&gt;&lt;li&gt;&lt;span&gt;•&lt;/span&gt;&lt;span&gt;&lt;div&gt;For &lt;em&gt;λ&lt;/em&gt;-generated &lt;strong&gt;W&lt;/strong&gt;-kernels &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;i&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, if &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;mo&gt;⊈&lt;/mo&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; then there exists &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;K&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mn&gt;3&lt;/mn&gt;&lt;/m","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"363 ","pages":"Article 109233"},"PeriodicalIF":0.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143352714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Identities for Whitehead products and infinite sums Whitehead积与无穷和的恒等式
IF 0.6 4区 数学
Topology and its Applications Pub Date : 2025-01-27 DOI: 10.1016/j.topol.2025.109232
Jeremy Brazas
{"title":"Identities for Whitehead products and infinite sums","authors":"Jeremy Brazas","doi":"10.1016/j.topol.2025.109232","DOIUrl":"10.1016/j.topol.2025.109232","url":null,"abstract":"<div><div>Whitehead products and natural infinite sums are prominent in the higher homotopy groups of the <em>n</em>-dimensional infinite earring space <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>n</mi></mrow></msub></math></span> and other locally complicated Peano continua. In this paper, we derive general identities for how these operations interact with each other. As an application, we consider a shrinking wedge <figure><img></figure> of finite <span><math><mo>(</mo><mi>n</mi><mo>−</mo><mn>1</mn><mo>)</mo></math></span>-connected CW-complexes and compute the infinite-sum closure <span><math><msub><mrow><mi>W</mi></mrow><mrow><mn>2</mn><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo></math></span> of the set of Whitehead products <span><math><mo>[</mo><mi>α</mi><mo>,</mo><mi>β</mi><mo>]</mo></math></span> in <span><math><msub><mrow><mi>π</mi></mrow><mrow><mn>2</mn><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msub><mrow><mo>(</mo><mi>X</mi><mo>)</mo></mrow></math></span> where <span><math><mi>α</mi><mo>,</mo><mi>β</mi><mo>∈</mo><msub><mrow><mi>π</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo></math></span> are represented in respective sub-wedges that meet only at the basepoint. In particular, we show that <span><math><msub><mrow><mi>W</mi></mrow><mrow><mn>2</mn><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo></math></span> is canonically isomorphic to <span><math><msubsup><mrow><mo>∏</mo></mrow><mrow><mi>j</mi><mo>=</mo><mn>1</mn></mrow><mrow><mo>∞</mo></mrow></msubsup><mrow><mo>(</mo><msub><mrow><mi>π</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>(</mo><msub><mrow><mi>X</mi></mrow><mrow><mi>j</mi></mrow></msub><mo>)</mo><mo>⊗</mo><msub><mrow><mo>∏</mo></mrow><mrow><mi>k</mi><mo>&gt;</mo><mi>j</mi></mrow></msub><msub><mrow><mi>π</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>(</mo><msub><mrow><mi>X</mi></mrow><mrow><mi>k</mi></mrow></msub><mo>)</mo><mo>)</mo></mrow></math></span>. The insight provided by this computation motivates a conjecture about the isomorphism type of the elusive groups <span><math><msub><mrow><mi>π</mi></mrow><mrow><mn>2</mn><mi>n</mi><mo>−</mo><mn>1</mn></mrow></msub><mo>(</mo><msub><mrow><mi>E</mi></mrow><mrow><mi>n</mi></mrow></msub><mo>)</mo></math></span>, <span><math><mi>n</mi><mo>≥</mo><mn>2</mn></math></span>.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"362 ","pages":"Article 109232"},"PeriodicalIF":0.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On strong generalized topology generated by the porosity 由孔隙度产生的强广义拓扑
IF 0.6 4区 数学
Topology and its Applications Pub Date : 2025-01-23 DOI: 10.1016/j.topol.2025.109223
Jacek Hejduk, Piotr Nowakowski
{"title":"On strong generalized topology generated by the porosity","authors":"Jacek Hejduk,&nbsp;Piotr Nowakowski","doi":"10.1016/j.topol.2025.109223","DOIUrl":"10.1016/j.topol.2025.109223","url":null,"abstract":"<div><div>This paper presents the strong generalized topology of sets having the property that every element is the porosity point of its complement. In the frame of generalized topology the fundamental topological properties are investigated including the separation axioms. There is the aspect of delving into the study of continuity including the notion of the approximate continuity.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"362 ","pages":"Article 109223"},"PeriodicalIF":0.6,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Countably tight, zero-dimensional and totally disconnected dense subspaces of Cp(X) Cp(X)的可数紧、零维、完全不连通的稠密子空间
IF 0.6 4区 数学
Topology and its Applications Pub Date : 2025-01-21 DOI: 10.1016/j.topol.2025.109220
Joel Aguilar-Velázquez , Reynaldo Rojas-Hernández
{"title":"Countably tight, zero-dimensional and totally disconnected dense subspaces of Cp(X)","authors":"Joel Aguilar-Velázquez ,&nbsp;Reynaldo Rojas-Hernández","doi":"10.1016/j.topol.2025.109220","DOIUrl":"10.1016/j.topol.2025.109220","url":null,"abstract":"<div><div>In this paper we prove that under <em>CH</em> there exists a space <em>X</em> such that <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo></math></span> does not admit dense subspaces of countable tightness, partially answering Problem 1 of <span><span>[13]</span></span>. We prove that if <em>X</em> has cardinality at most continuum, then <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>(</mo><mi>X</mi><mo>)</mo></math></span> contains a dense zero-dimensional subspace and a dense totally disconnected non zero-dimensional subspace. We also provide an example of a compact space <em>X</em> such that <span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>p</mi></mrow></msub><mo>(</mo><mi>X</mi><mo>,</mo><mn>2</mn><mo>)</mo></math></span> is exponentially separable but <em>X</em> is not Corson compact.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"362 ","pages":"Article 109220"},"PeriodicalIF":0.6,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143135535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Brouwer's fixed-point theorem on the finite product of compact linearly ordered topological spaces 紧线性有序拓扑空间有限积上的布劳威尔不动点定理
IF 0.6 4区 数学
Topology and its Applications Pub Date : 2025-01-21 DOI: 10.1016/j.topol.2025.109221
Tetsuya Ishiu
{"title":"Brouwer's fixed-point theorem on the finite product of compact linearly ordered topological spaces","authors":"Tetsuya Ishiu","doi":"10.1016/j.topol.2025.109221","DOIUrl":"10.1016/j.topol.2025.109221","url":null,"abstract":"<div><div>We shall show that the finite product of compact connected linearly ordered topological spaces satisfies Brouwer's fixed-point theorem and the Poincaré-Miranda Theorem.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"362 ","pages":"Article 109221"},"PeriodicalIF":0.6,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143135528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Smooth finite group actions on homology six-spheres with odd Euler characteristic fixed point sets 具有奇欧拉特征不动点集的同调六球光滑有限群作用
IF 0.6 4区 数学
Topology and its Applications Pub Date : 2025-01-20 DOI: 10.1016/j.topol.2025.109219
Shunsuke Tamura
{"title":"Smooth finite group actions on homology six-spheres with odd Euler characteristic fixed point sets","authors":"Shunsuke Tamura","doi":"10.1016/j.topol.2025.109219","DOIUrl":"10.1016/j.topol.2025.109219","url":null,"abstract":"<div><div>In this paper, we prove that if a finite group <em>G</em> acts smoothly and effectively on an integral homology 6-sphere and the <em>G</em>-fixed-point set has an odd Euler characteristic, then the acting group <em>G</em> is isomorphic to either the alternating group <span><math><msub><mrow><mi>A</mi></mrow><mrow><mn>5</mn></mrow></msub></math></span> on five letters, the symmetric group <span><math><msub><mrow><mi>S</mi></mrow><mrow><mn>5</mn></mrow></msub></math></span> on five letters, or the Cartesian product <span><math><msub><mrow><mi>A</mi></mrow><mrow><mn>5</mn></mrow></msub><mo>×</mo><msub><mrow><mi>C</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span>, where <span><math><msub><mrow><mi>C</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> is a group of order 2, and the <em>G</em>-fixed-point set consists of precisely one point.</div></div>","PeriodicalId":51201,"journal":{"name":"Topology and its Applications","volume":"362 ","pages":"Article 109219"},"PeriodicalIF":0.6,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143134511","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"数学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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